/*
 * Created on Apr 5, 2005
 * Created by Alon Rohter
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package com.aelitis.azureus.core.peermanager.unchoker;

import java.util.ArrayList;
import java.util.Iterator;

import org.gudy.azureus2.core3.disk.DiskManager;
import org.gudy.azureus2.core3.peer.PEPeer;

/**
 * Unchoker implementation to be used while in downloading mode.
 */
public class DownloadingUnchoker implements Unchoker {

    private ArrayList<PEPeer> chokes = new ArrayList<PEPeer>();
    private ArrayList<PEPeer> unchokes = new ArrayList<PEPeer>();

    protected DownloadingUnchoker() {
        /* nothing */
    }

    public boolean isSeedingUnchoker() {
        return (false);
    }

    public ArrayList<PEPeer> getImmediateUnchokes(int max_to_unchoke, ArrayList<PEPeer> all_peers) {
        ArrayList<PEPeer> to_unchoke = new ArrayList<PEPeer>();

        // count all the currently unchoked peers
        int num_unchoked = 0;
        for (int i = 0; i < all_peers.size(); i++) {
            PEPeer peer = all_peers.get(i);
            if (!peer.isChokedByMe())
                num_unchoked++;
        }

        // if not enough unchokes
        int needed = max_to_unchoke - num_unchoked;
        if (needed > 0) {
            for (int i = 0; i < needed; i++) {
                PEPeer peer = UnchokerUtil.getNextOptimisticPeer(all_peers, true, true);
                if (peer == null)
                    break; // no more new unchokes avail
                to_unchoke.add(peer);
                peer.setOptimisticUnchoke(true);
            }
        }

        return to_unchoke;
    }

    public void calculateUnchokes(int max_to_unchoke, ArrayList<PEPeer> all_peers, boolean force_refresh, boolean check_priority_connections,
            boolean do_high_latency_peers) {
        int max_optimistic = ((max_to_unchoke - 1) / 10) + 1; // one optimistic unchoke for every 10 upload slots

        ArrayList<PEPeer> optimistic_unchokes = new ArrayList<PEPeer>();
        ArrayList<PEPeer> best_peers = new ArrayList<PEPeer>();
        long[] bests = new long[max_to_unchoke]; // ensure we never pick more slots than allowed to unchoke

        // get all the currently unchoked peers
        for (int i = 0; i < all_peers.size(); i++) {
            PEPeer peer = all_peers.get(i);

            if (!peer.isChokedByMe()) {
                if (UnchokerUtil.isUnchokable(peer, true)) {
                    unchokes.add(peer);
                    if (peer.isOptimisticUnchoke()) {
                        optimistic_unchokes.add(peer);
                    }
                } else { // should be immediately choked
                    chokes.add(peer);
                }
            }
        }

        if (!force_refresh) { // ensure current optimistic unchokes remain unchoked
            for (int i = 0; i < optimistic_unchokes.size(); i++) {
                PEPeer peer = optimistic_unchokes.get(i);

                if (i < max_optimistic) {
                    best_peers.add(peer); // add them to the front of the "best" list
                } else { // too many optimistics
                    peer.setOptimisticUnchoke(false);
                }
            }
        }

        // fill slots with peers who we are currently downloading the fastest from
        int start_pos = best_peers.size();
        for (int i = 0; i < all_peers.size(); i++) {
            PEPeer peer = all_peers.get(i);

            if (peer.isInteresting() && UnchokerUtil.isUnchokable(peer, false) && !best_peers.contains(peer)) { // viable peer found
                long rate = peer.getStats().getSmoothDataReceiveRate();
                if (rate > 256) { // filter out really slow peers
                    UnchokerUtil.updateLargestValueFirstSort(rate, bests, peer, best_peers, start_pos);
                }
            }
        }

        // if we havent yet picked enough slots
        if (best_peers.size() < max_to_unchoke) {
            start_pos = best_peers.size();

            // fill the remaining slots with peers that we have downloaded from in the past
            for (int i = 0; i < all_peers.size(); i++) {
                PEPeer peer = all_peers.get(i);

                if (peer.isInteresting() && UnchokerUtil.isUnchokable(peer, false) && !best_peers.contains(peer)) { // viable peer found
                    long uploaded_ratio =
                            peer.getStats().getTotalDataBytesSent() / (peer.getStats().getTotalDataBytesReceived() + (DiskManager.BLOCK_SIZE - 1));
                    // make sure we haven't already uploaded several times as much data as they've sent us
                    if (uploaded_ratio < 3) {
                        UnchokerUtil.updateLargestValueFirstSort(peer.getStats().getTotalDataBytesReceived(), bests, peer, best_peers, start_pos);
                    }
                }
            }
        }

        if (force_refresh) {
            // make space for new optimistic unchokes
            while (best_peers.size() > max_to_unchoke - max_optimistic) {
                best_peers.remove(best_peers.size() - 1);
            }
        }

        // if we still have remaining slots
        while (best_peers.size() < max_to_unchoke) {
            PEPeer peer = UnchokerUtil.getNextOptimisticPeer(all_peers, true, true); // just pick one optimistically
            if (peer == null)
                break; // no more new unchokes avail

            if (!best_peers.contains(peer)) {
                best_peers.add(peer);
                peer.setOptimisticUnchoke(true);
            } else {
                // we're here because the given optimistic peer is already "best", but is choked still,
                // which means it will continually get picked by the getNextOptimisticPeer() method,
                // and we'll loop forever if there are no other peers to choose from
                peer.sendUnChoke(); // send unchoke immediately, so it won't get picked optimistically anymore
                // all_peers.remove( peer ); //remove from all_peers list, so it won't get picked optimistically anymore //TODO
            }
        }

        // update chokes
        for (Iterator<PEPeer> it = unchokes.iterator(); it.hasNext();) {
            PEPeer peer = it.next();

            if (!best_peers.contains(peer)) { // should be choked
                if (best_peers.size() < max_to_unchoke) { // but there are still slots needed (no optimistics avail), so don't bother choking them
                    best_peers.add(peer);
                } else {
                    chokes.add(peer);
                    it.remove();
                }
            }
        }

        // update unchokes
        for (int i = 0; i < best_peers.size(); i++) {
            PEPeer peer = best_peers.get(i);

            if (!unchokes.contains(peer)) {
                unchokes.add(peer);
            }
        }

        if (do_high_latency_peers) {

            UnchokerUtil.doHighLatencyPeers(chokes, unchokes, true);
        }
    }

    public ArrayList<PEPeer> getChokes() {
        ArrayList<PEPeer> to_choke = chokes;
        chokes = new ArrayList<PEPeer>();
        return to_choke;
    }

    public ArrayList<PEPeer> getUnchokes() {
        ArrayList<PEPeer> to_unchoke = unchokes;
        unchokes = new ArrayList<PEPeer>();
        return to_unchoke;
    }

}
